Mr Grantham points out that half of nearby Mali - admittedly the sparsely populated Saharan half - was recently briefly overrun by militants affiliated with al-Qaeda, and he warns that Morocco itself may one day become the scene of rising social tensions, terrorism or revolt.

"I would almost guarantee to you that the major militaries of this world are well aware of this problem.

"They would not allow Morocco to become a hopelessly failed state," he says reassuringly.

"You don't want to look forward to the great fertiliser wars of 2042."

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